AES - Red screen on boot - Work RAM fault?

Joined
Aug 21, 2019
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4
Good morning Neo Geo fans. I’ve recently bought an old AES, the Neo-AES3-6 version. I get the red screen on boot which I understand from other threads means a work RAM error. I’ve cleaned the board, checked all the traces and continuity between RAM chips and the CPU and all seems good. So my question is what can I do next (I’m mediocre at best with a soldering iron) and if the answer is “send it to an expert to repair”, who would you recommend in the UK. I live in Essex. Thanks for any help and apologies as a first time poster of I’ve missed anything I should know.
 

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maki

Edo Express Delivery Guy
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Jan 1, 2022
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Yeah it should be a work RAM fault, if you can get a diagnose BIOS, it could maybe tell you more

the work RAM on the AES3-6 is next to the reset button, careful with hot air there

there is a high chance that the RAM is fine but the traces are rotten, these should always be checked

the scene seems to be quite vivid in the UK, I'm in Germany so I don't have any particular names but there should be plenty of console repair people that have experience with Neo Geo.
 

Neo Alec

Ned's Ninja Academy Dropout
20 Year Member
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Dec 7, 2000
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11,927
Yeah, the traces around the reset button can be the first to go bad, since moisture can more easily get in that area. Definitely look there and test the traces in that area with a multimeter. You'll need to jump any broken traces with a wire, which isn't very difficult.
 
Joined
Aug 21, 2019
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I used a multimeter in continuity mode and all traces seemed to either successfully link one ram chip to the other or across to the CPU. However I will double check given advice that a bad trace is more likely than a bad chip.
 

maki

Edo Express Delivery Guy
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Jan 1, 2022
Posts
332
here is a pic of the backup RAM on an MVS, wiring is the same for the work RAM (AES don't have back RAM)

if you can get a Diag BIOS, it would help to see if a chip is dead, can't be written or if the read value was wrong
each of the yellow address lines are connected to each other on both IC if they have the same number, A0 on IC 1 is connected to A0 on IC 2 etc.

As you can see there is traces underneath the IC (and on the other side of the PCB), this pic can help you testing without removing the ICs

the orange markings will go to a different IC than U17, as this is the marking on the MVS for the backup RAM, should be going to a 74HC32 that controls which IC is actually selected for /CE and /WE

MV1FZ Backup RAM.jpg
 
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